This application claims the priority of German Patent Application No. 197 33 189.0, filed Jul. 31, 1997, and German Patent Application No. 197 36 064.5, filed Aug. 20, 1997, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a defect recognition device for internal-combustion engines and to a process for operating an internal-combustion engine.
In general, it should be possible to recognize defects in internal-combustion engines reliably and at reasonable cost. For recognizing defects, defect recognition devices are provided, for example, which are assigned to a component of the internal-combustion engine and are capable of recognizing a defect or a defective action with respect to this component. It is obvious that in the case of such an approach a separate defect recognition device is required for every component which may possibly generate a defect.
From German Patent Document DE 195 13 156 C1, a turbo-charged internal-combustion engine is known which has a defect recognition device in which a change-over takes place from a controlling of the fed air to a timing of the fed air when a one-sided defect is recognized in one of the exhaust gas trains. For recognizing a defect in one of the exhaust gas trains, it is suggested to monitor the internal-combustion engine to determine whether an accumulation of engine cutouts is occurring at one of the cylinder banks.
Furthermore, vehicles are known--for example, the Porsche 911 turbo--which have two separate exhaust gas trains and in which a lambda control is used within the scope of the fuel apportioning (metering). For the lambda control, a separate lambda probe is provided in each exhaust gas train. However, the fuel apportioning and the lambda control take place for the internal-combustion engine as a whole which drives the vehicle. In the case of a lambda value of approximately 1.0, the used lambda probes have a signal jump so that only a lambda control to the desired 1.0 value is possible.
In contrast to the state of the art, it is an object of the invention to provide an internal-combustion engine with an improved defect recognition device and process.
According to the invention, this object is achieved by a defect recognition device for an internal-combustion engine having at least two exhaust gas trains, one lambda probe respectively in the exhaust gas trains, a joint measuring device for detecting the supplied air, and a joint timing device for metering the fuel. The lambda probes generate a continuous signal for the lambda value of the exhaust gas. The defect recognition device recognizes a defect when the signal supplied by the lambda probes deviate from one another. A process according to the invention achieves the above objects by operating an internal-combustion engine, by (1) determining the lambda value of the exhaust gas for each exhaust gas train; (2) calculating the difference between the lambda values; (3) comparing the difference with a limit value; and (4) emitting a defect signal when the difference is larger than a limit value.
The invention is based on the recognition that, in the case of an internal-combustion engine where the apportioning of the fuel supply takes place for the internal-combustion engine as a whole (that is, not specifically for one part of the internal-combustion engine), a number of components affect the volumetric efficiency of the internal-combustion engine or other quantities influencing the combustion process. If these components are then provided in a multiple manner; in which case each of the components is independently assigned to a part of the internal-combustion engine, in the case of an internal-combustion engine with separate exhaust gas trains, defects can be recognized in that the exhaust gas composition of the individual exhaust gas trains is determined and is compared with the corresponding value of the other exhaust gas trains. If one of the exhaust gas trains deviates in this comparison, a conclusion can be drawn that a defect exists in this exhaust gas train or the constructional elements assigned to this exhaust gas train. Constructional elements which are accessible to such a defect recognition are, for example, fuel injection nozzles, adjusting devices for the valve stroke, adjusting devices for the position of the camshafts, ignition devices as well as all constructional elements penetrated by the exhaust gas flow.
According to the invention, it is therefore provided to use lambda probes in the case of an internal-combustion engine of the above-mentioned type which generate a continuous signal for the lambda value of the exhaust gas. The error recognition device will then recognize a defect when the signals supplied by the lambda probes deviate from one another. The lambda probes used so far do not generate a continuous signal, but rather a signal jump at a lambda value of approximately 1.0. The special advantage according to the invention is therefore the use of the continuously operating lambda probes by which it is now possible to carry out a comparison of the signals supplied by the lambda probes and to draw a conclusion from them concerning a different exhaust gas composition in the individual exhaust gas trains. Furthermore, according to the invention, a plurality of defects can be recognized by use of a single defect recognition device and a single process for recognizing defects.
Further advantageous developments of the invention are described herein.
Thus, it is provided to use the described defect recognition device in the case of a turbocharged internal-combustion engine which has separate exhaust gas trains and, in addition, as a function of a defect signal, switches from a controlling of the rate of air flow to a timing of the rate of air flow. In the case of such an internal-combustion engine, as known, for example, from German Patent Document DE 195 13 156 C1, by means of the invention, the defect signal required for a switch-over can be generated in a simple manner. Assuming in the case of such an internal-combustion engine that a lambda control is already used for the fuel apportioning, the lambda probes required for this lambda control can be used by the device for the apportioning of fuel as well as by the defect recognition device according to the invention so that no additional costs will arise.
To the extent that, in the case of an internal-combustion engine, devices are provided for adjusting the relative position of camshafts or for adjusting the valve stroke of inlet valves and/or outlet valves, a defect in one of these adjusting devices can be determined in a particularly simple manner. This is because whether the defect recognition device according to the invention emits a defect signal is examined immediately after an operating of the adjusting device. If such an examination reveals that a defect signal occurs as the reaction to the operating of the adjusting element, then the conclusion can be drawn that the defect was triggered by the just operated adjusting device and the defect can be assigned to this adjusting device.